Declined conveyors are well known. They are used in many different applications, such as to convey packages to loading bays for loading onto trucks. Declined conveyors may be powered conveyors, such as declined belt conveyors. Declined conveyors may be non-powered, such as gravity conveyors comprising skate wheels or rollers which are free to rotate. Gravity conveyors can function to accumulate packages, eliminating the need for a separate accumulation conveyor. While gravity conveyors are less expensive than powered declined conveyors, their free flowing nature presents flow control problems that can result in impacts between packages thereby interrupting flow, causing jams, misorienting packages, causing package damage or other interruptions to product flow.
The pitch of a gravity conveyor must be great enough for light weight packages to spin the rollers, as is necessary to continue traveling down the conveyor, yet small enough to minimize heavy cartons from gaining too much momentum and crashing into other packages. A gravity conveyor may lack sufficient control to avoid overfeeding the conveyor which carries packages from the lower end of the gravity conveyor.
In order for an initial package to continue traveling down a gravity conveyor, it must overcome the inertia of each roller or wheel it contacts and start it spinning, which removes energy from the package, slowing it down. If a trailing package is following closely enough, the rollers or wheels may still be spinning, so the trailing package does not have to start the rollers or wheels, and thus its speed does not decrease as much as the first package (and may actually increase). Depending on spacing, subsequent packages may be accelerated by the spinning rollers or wheels, and impact the leading packages.
It is known to provide spaced apart, constant speed driven rollers as part of the conveying surface, generally perpendicular to the direction of package travel, acting as a brake. However, while relatively inexpensive, such a configuration often does not provide enough control.
It is also known to provide brakes to stop a group of rollers from spinning. Such brakes typically act on the lower surface of the rollers. However, light packages which are stopped thereby may have difficulty restarting.
The present invention represents an economical solution to controlling package flow down declined conveyors.